Sound suppressing device comprising elastic tubular sleeve for air actuated percussive type tools



1 6 8 R 2 U Tm MT m My T E V GT. sms D WM. LIC o E N P o Y E R M .I w EC A G Dec. 28, 1965 SOUND SUPPRESSIN SLEEVE FOR AIR Filed Sept. 13, 1963 2 Sheets-Sheet 1 INVENTOR. JOHN W REYNOLDS Aftorno y J. W. REYNOLDS Dec. 28, 1965 3,225,861

SOUND SUPPRESSING DEVICE COMPRISING ELASTIC TUBULAR SLEEVE FOR AIR ACTUATED PERCUSSIVE TYPE TOOLS Filed Sept. 13, 1965 2 Sheets-Sheet 2 FIG. 6

sou/v0 LEVEL SPECTROGRAM D m w w 7 TOTAL 7200 2400 4800 NOISE LEVEL m m u n m 9 a 7 ,WQQQDQQE Named wk m mmamfi FREQUENCY RANGES (CYCLES PER SECOND) INVENTOR JOHN W REYNOLDS Attorney United States Patent 3 225 861 SOUND SUPPRESSIP IG l)EVICE COMPRISING ELASTIC TUBULAR SLEEVE FOR AIR AC- TUATED PERCUSSIVE TYPE TOOLS John W. Reynolds, Kimberley, British Columbia, Canada,

This invention relates to a sound suppressing device for air actuated percussive type tools and machines such as rock drills, air hammers and the like.

Pneumatic percussive type tools or machines are well known and are widely used in industry. High frequency blows are delivered by a hammer, which is a free piston working inside the cylinder of the tool or machine. The compressed air which actuates the piston is fed alternately to the front and back faces of the piston. Air is exhausted, while still at a pressure substantially higher than atmospheric, at the end of each motion of the piston, by having a face of the piston pass an exhaust port in the side of the cylinder. This compressed air is released explosively. Most of the sound emitted by the pneumatic percussive type tools is a result of the explosive release of the compressed air and the percussion of the piston against the tool steel.

Air actuated, percussive type tools, while very satisfactory and eflicient insofar as their operation is concerned, have the disadvantage that the sound level of the exhausted air is sufficiently high that the noise is annoying, at least to those exposed to it for prolonged periods of time. Also, the noise prevents conversation in the environment of the tool. A further disadvatage is the fog or mist formed by the exhaust gas in the environment of the tool is a nuisance and may be a hazard.

I have found that the sound level of the exhaust air and the hammer noise of the percussive type tools or machines can be reduced to the extent that conversation can be carried on in the environment of the tool and the fog or mist created by the exhausting air is eliminated without in any way interfering with the normal, efficient operation of the tool by enclosing the cylinder section and the exhaust port in a muffler formed of expansible, elastic sound absorbing material.

The sound suppressing device of this invention is effective for lowering the sound intensity level of pneumatically actuated percussive type tools. The device collects the explosively released exhaust air in an expansible enclosure and releases it as a pulsating stream. Also, by enclosing that part of the tool which contains the piston and tool steel and that part wherein the exhaust port is located, the device attenuates the sound produced by the percussion of the piston against the tool steel.

The sound suppressing device of this invention is described in detail hereinafter as applied to a percussive type rock drill used for drilling blast holes in rock. It will be understood, however, that the device can be employed with other types of air actuated percussive types of tools of which the sound or noise of operation is a problem.

An understanding of the sound suppressing device of this invention can be obtained from the following detailed ice description, reference being made to the accompanying drawings in which:

FIGURE 1 is a perspective view of a rock drill assembly illustrated by phantom lines showing a sectional view of the sound suppressing device in place and enclosing the cylinder section and exhaust ports;

FIGURE 2 is a side elevation of the cylinder portion of the drill assembly showing the air exhaust ports and the spaced collar-s;

FIGURE 3 is a side elevation of the sleeve of the sound suppressing device showing one method for bolding the sleeve in place;

FIGURE 4 is an end view of a modified rear collar;

FIGURE 5 is a partial View of a ducted sleeve; and

FIGURE 6 is a graph illustrating the sound effects of the conventional rock drill without the sound suppressing device, with the sound suppressing device over the exhaust ports only, and with the sound suppressing device over the cylinder portion of the drill and the exhaust orts. p Like reference characters refer to like parts throughout the description of the invention and the drawing.

The drill assembly illustrated in FIGURE 1 is of a conventional, air actuated, percussive type for drilhng blast holes in a mining operation. It comprises an adjustable supporting assembly 10, an air cylinder 11 having an air inlet port 12, at least one air exhaust port 14, an air actuated reciprocating piston, not shown, in the cylinder, and a drill rod assembly 15 actuated by the piston. Water is supplied to the assembly through inlet .16. The part of this assembly with which the sound suppressing device of this invention is associated is the cylinder 11 and exhaust port 14, illustrated in larger detail in FIGURE 2.

A pair of collars, bushings or the like annular elements 20-21 is fitted in spaced relation on the cylinder, preferably at or adjacent to the ends thereof, with the exhaust port 14 between them. The collar 20 is located at or adjacent to the rear end of the cylinder and is referred to herein as the rear collar. The collar 21 is nearest the chuck which holds the drill rod assembly and is referred to as the forward collar. If necessary, the portions of the cylinder on which the collars are mounted can be built to circular shape according to known procedures to form annular elements but normally the collars are molded to fit the cylinder. If the shape of the tool so provides, the collars can be dispensed with.

FIGURE 3 illustrates a circular sleeve 22 of expansible material which is extended over the collars 2021 and is held in place by the boss 18 which projects through a slot 17 in the sleeve 22. The operating handle 13 which is inserted through the boss 18 above the sleeve 22 serves to hold the sleeve in place.

The collars 20-21 should have the same outside circumference as the inside circumference of the sleeve 22 to ensure a close, friction fit between the parts. The outer surfaces of the collars and the inner surface of the sleeve are preferably circular but can have an elliptical or other convenient shape provided that a snug fit is obtained.

The sleeve 22 encloses the exhaust port 14. The exhaust air builds up pressure in the sleeve in the confined space or enclosure between the collars and is released by expansion of the sleeve, creating a small gap between the sleeve and the end collars. The sleeve releases the exhaust air relatively slowly and quietly from the enclosure in contrast to the explosive release of the exhaust air at the exhaust port from the air cylinder. It will be evident from the foregoing description that sleeve 22 stretchably embraces the collars or like annular elements; i.e. sleeve 22 which makes a snug fit with collars 20-21 is capable of being stretched to form a gap between the sleeve and collars.

The sleeve 22 can be made to release the exhaust air under conditionos which suit the particular drill or tool on which it is mounted. The exhaust air can be released from the enclosure by simply expanding the sleeve under pressure, thereby creating a small gap between the sleeve and collars. The exhaust air can be released at one end only by making the tension greater between the sleeve and the collar at the end where no escape is desired. Stresses in the sleeve can be minimized by leaving slots, as indicated by numerals 30 and 30a, FIGURE 4, through which it is intended to permit exhaust air to escape. I have found that there will be little loss in noise suppression qualities of the muffler providing such slots are located on the side of the cylinder opposite to the exhaust ports. Alternatively, stresses in the sleeve can be minimized by attaching a short duct, as indicated by numeral 31, FIGURE 5, at the end of the sleeve where escape is intended, so as to carry the escaping air over the end collar without stretching the sleeve too violently.

The collars 20-21 can be formed of any suitable material. The sleeve 22 can be formed of any suitable, expansible, elastic material such as natural or synthetic rubber. A satisfactory arrangement for the sleeve is natural rubber, bondedin two layers to a thickness of about one quarter inch. In the tool illustrted in the drawings, the sleeve is held in position by the boss for a handle which projects through the sleeve. In the absence of such a projection, the sleeve may be held in place by any convenient means such as a stud and spacer. The forward end of the sleeve where it embraces the forward collar may be reinforced with a small band of wire or cordembedded between the layers.

The rock drill is actuated by high pressure air, conventionally of the order of from about 85 to 100 pounds per square inch or higher. Air pressure builds up in the sleeve during the operation of the drill. This pressure is relieved by leakage of air as a pulsating stream between the sleeve and at least one of the collars 20-21 and through the notches or slots 30-30a, or duct 31, if provided.

The sound suppressing device for drills described above is surprisingly effective. Sound suppression is effected by muffling the noise of the exhaust and by attenuating the sound produced by the percussion of the piston against the tool steel. Air is released from the sleeve 22 as a pulsating stream without loss of efficiency of the drill in terms of feet per minute penetration of the drill steel into the rock. The sound suppressing effect of the device is illustrated by FIGURE 6, in which:

(1) The dotted line illustrates the sound level when operating the drill without any sound suppressing attachment; I

(2) The broken line illustrates the sound level when operating the drill with the sound suppressing device over the exhaust ports only;

(3) The solid line illustrates the sound lever when operating a drill with the sound suppressing device in place over both the exhaust ports and cylinder containing the piston hammer. The drill was operated at a penetration speed of 12 inches per minute, with air supplied at 80-83 pounds per square inch, and water supplied at 41 pounds per square inch. Air consumption was 125 cubic feet per minute.

Noise measurements were made in the operators hearing zone.

In each instance, the sound level is indicated in terms of decibels for a stated frequency range in terms of cycles per second, c.p.s. The frequency ranges used, such as 20 to 75 c.p.s., 75 to c.p.s., may be referred to as wave or octave bands. The graph is marked according to recognized octave bands starting at 20-75 c.p.s. and ending at 4800-l0,000 c.p.s.

The graph clearly shows a marked reduction in sound intensity levels with the sound suppressing device of this invention attached to the air cylinder and enclosing the air exhaust port or ports. In fact, the loudest sound was identified as that of the drill contacting the rock. It was possible to carry on a. conversation with the drill in operation; no difficulty was encountered with ice formation; and the fog and mist around the drill assembly were appreciably reduced.

' What I claim as new and desire to protect by Letters Patent of the United States is:

1. A sound suppressing device for an air actuated percussive type tool having an air cylinder, a piston therein, an air inlet port and at least one air exhaust port, said device comprising a pair of spaced annular elements on said cylinder with said air exhaust port therebetween, an expansible elastic tubular sleeve stretchably embracing said annular elements in close fitting relationship and standing substantially free of the cylinder for forming an enclosure for receiving air from said air exhaust port, and for defining a gap between the sleeve and at least one of said annular elements for escape of said air as a pulsating stream, and means for holding said sleeve in place.

2. In a sound suppressing device as claimed in claim 1, at least one of said annular elements having a slot formed transversely in its outer periphery on a side remote from said air exhaust port defining a duct between said annular element and sleeve for facilitating the discharge of exhaust air between said collar and sleeve.

3. In a sound suppressing device as claimed in claim 1, said sleeve having a duct formed thereon adapted to discharge a portion only of the exhaust air.

4. A sound suppressing device for an air actuated percussive type tool having an air cylinder, a piston therein, an air inlet port and at least one air exhaust port, said device comprising a pair of axially spaced annular elements on said cylinder with said air exhaust port therebetween, an elongated tubular sleeve formed of an elastic material stretchably embracing said annular elements in close fitting relationship for defining a gap between the sleeve and at least one of the annular elements for escape of exhaust air as a pulsating stream, said sleeve defining an annular space between said cylinder and said annular elements, and means for holding said sleeve in its operative position.

5. A sound suppressing device for an air actuated percussive type tool having an air cylinder, an air inlet port and at least one air exhaust port, said device comprising a rear collar and a forward collar mounted on said cylinder on either side of said exhaust port adapted to fit the configuration of said cylinder, a tubular sleeve formed of an expansible elastic material stretchably embracing the collars in tight fitting relationship for defining an annular space about the cylinder between said collar and for defining a gap between the sleeve and rear collar to release exhaust. air as a pulsating stream during operation of the percussive type tool, and means disposed between the collarsfor anchoring the sleeve in its operative position relative to the collars.

6. In a sound suppressing device as claimed in claim 5, at lea-st one of said collars having a slot formed transversely in its outer periphery on a side remote from said air exhaust port defining a duct between said collar and sleeve for facilitating the discharge of ex-r haust air between said collar and sleeve.

7. In a sound suppressing device as claimed in claim 5, said sleeve having a duct formed thereon adapted to discharge a portion only of the exhaust air.

References Cited by the Examiner UNITED STATES PATENTS 1,115,704 11/1914 Manes 181-36 2,561,726 7/1951 Cherain a- 18136 932,373 7/1963 Great Britain.

LEO SMILOW, Primary Examiner. 

1. A SOUND SUPPRESSING DEVICE FOR AN AIR ACTUATED PERCUSSIVE TYPE TOOL HAVING AN AIR CYLINDER, A PISTON THEREIN, AN AIR INLET PORT AND AT LEAST ONE AIR EXHAUST PORT, SAID DEVICE COMPRISING A PAIR OF SPACED ANNULAR ELEMENTS ON SAID CYLINDER WITH SAID AIR EXHAUST PORT THEREBETWEEN, AN EXPANSIBLE ELASTIC TUBULAR SLEEVE STRETCHABLY EMBRACING SAID ANNULAR ELEMENTS IN CLOSE FITTING RELATIONSHIP AND STANDING SUBSTANTIALLY FREE OF THE CYLINDER FOR FORMING AN ENCLOSURE FOR RECEIVING AIR FROM SAID AIR EXHAUST PORT, AND FOR DEFINING A GAP BE- 